Spark plug



R. H. MOTH SPARK PLUG Arifi W, 1951 2 Sheets-Sheet 1 Filed Dec. 30, 1948 INVENTOR.

ROBERT 7. ATTORNEY R. H. MOTH SPARK PLUG April 10, 1951 2 Sheets-Sheet 2 Filed Dec. 50, 1948 INVENTOR. ROBERT I 1. MOTH BYZZZKQJ 5/.

ATTORNEY Patented Apr. 10, 1951 SPARK PLUG Robert H. Moth, -Chicago, Ill., assignor to The Pure Oil-Company, Chicago, 111., a corporation of Ohio Application December 30,1948, Serial N0.'68,295

. 1 This invention relatesto ignition systems for internal combustion engines andamoreparticu- .7 :Claims. (Cl. 123-169) larly, relates to a sparkz-plug --hav inga constant .gap between electrodes during extended periods of constant service.

During theoperation of an internalcombustion engine, particularlylarge stationary engines .used in industrialplants, the constant passage of current between the spark plug electrodes results in their edisintegration to such an extent'that their function may .be-seriously'impaired. Consequently, it is necessary to periodically check the sparkplugszas to'gapadjustment and general sparking characteristics. Inthe installation of 'newspark plugs some allowances-canbe made for, this electrode disintegration by ;adjustment at closer tolerance to overcome-the tendency of the spark gap' space torincrease, but such adjust- .ment is not a satisfactory solutionto theproblem becauseit changes: the generalspark density and intensity. Commercial engines operating continuously foraextended periods of time. are subject to serious shutdown delays-due to spark ,plug failure or maladjustment thereof. -Since many such industrial engines cannot be started again-with one man,it may be necessary .to call in acrew of .men for .thatoperation.

To meet these problems, I have devised a spark plug system of novel construction :which gives automatic adjustment or correction of the spark gap between the electrodes, thereby prolonging the inspection periods. and eliminating; frequent adjustments of the spark plug. As a consequence thereof, the general combustion conditions within the engine: cylinder are more uniform and engine performance is substantially constant. Also, longer life is imparted to the high tension coil because of the more substantially uniform spark gap conditions and resistance in the ignition system. Accordingly, -it is the primary object of my invention to having automatic self-adjusting electrodes.

A secondary object of my invention is to provide a spark; plug which will give longer service without the necessity of adjustment.

A third object of my invention is to provide a spark plug with electrodes which are held at a constant distance, from each otherby the positioning of a suitable non-conductor material therebetween.

A fourth object of my invention is to provide a spark plug, the electrodes of which are separated by a sapphire crystal.

Other objects and advantages of my invention will become apparentifrom the detailed JdiSCIO-g :surewh chtfollows-andzthe aCQ mpanying 51 in rOfwhich .-Figure lriS a longitudinal cross-,sectionaLyiew through the-center of one formof my sparkplug showing the permanent attachment of a nonconductive separator to the negative central electrode and impinging; against a recess within the positive electrode.

:Figure r2 is a fragmentary:verticahcrossesection showing another embodiment ofi my invenwtion .with the noneconductive .separator firmly .afiixedzwithin the positive electrodebodyrand impinging upon I a. recessryvithin the; negative: electrode.

.Figure 3 ,is, a. fragmentary vertical =cross,-sec tional View showing anothermodifica'tionof the non-conductive separator which may be -in-- corporated in my invention.

Figure 4 is. a vertical cross=sction illustrating another embodiment oftheinvention ,in which a manuallyadjustable negativeelectrode. maintains the. electrodes in contact with the. nonconductive. separator.

Figure 5 illustrates a zlongitudinal cross-sectional view of still another .embodimentof .my invention in which the negative electrode is spring loadedto, maintain contact upon the .nonconductive separator.

.- Referring to Figure 1, the numeral l represents van insulatorcomposed of the ,usual insulating material now commonly used in1spark. plugs. Insulator 1, maybe of ,any desiredshape .ordesignaslong as it functions .to efiiciently insulate the electrodes ;(yet to be'described) of thespark .plugfrom each other. Vertically through the center ofuinsulator l -isgfittedelectrode- 2 which vis formed-of any suitable electrical conductor material preferably metallic. Electrode :2 is

tightlygsealed within-insulator I to form a;gas-

tight construction. It is commonpractice to provide a spark plug mmoldthe insulator-material.-around the electrode 1 to tobtain the-close fit required to withstand the cylinder pressures encountered. The upper end of electrode 2 is threaded, and-fitted. thereon are .knurlednutj and cap nut 4 for the attachment of .the distributor -.-wire. 'The .top :body portion 5 and lower body portion ;6,. made of electrical 1 conducting -materialsuch as 1 steel or :brass, are

adapted to engageeach other by screw threads and bind upon heat resistant packing rings! to .form ,a-gasetight .sealon the outer periphery of the central; portion of the insulator.

terminusofelectrode Zcontains-recess- 8 in order .to @accommodate a cylindrical -non-conductive separator 9. 1.Non .conductive separator .;is

The lower tween the electrodes.

Figure 2. r a the recess I8 and recess or hole 2|), and the shape pointed at its lower terminus and fits into a cylindrical recess II], of lesser diameter than the separator 9, positioned at the end of electrode Electrode may be an integral part of lower body portion 6 or may, as shown in the drawing, be a separate piece tightly fitted in recess l2 of lower body portion 6. Electrode H is fitted into body portion 6 in such a manner as to impart a spring tension thereto when the separator 9 is placed between the two electrodes, thereby causing the separator 9 to be tightly held becomplished by bending electrode H to 'a position such that the endsof the two electrodes must be forced apart in order toaccommodate the separator between them.

It is known that a high tension spark when jumping across an air or vapor filled gap between electrodes takes the shortest metal to metal path and as the metal of the electrodes disintegrates over the metal area through which the spark passes, the gap will become increasingly larger. When gap space increases of approximately .020 inch or more are experienced, the spark intensity will decline or the spark will seek the next less resistive path offered by the system.

between the electrodes.

The fragmentary vertical cross-sectional view, Figure 2, is meant to show another embodiment of my invention in which the insulator is represented by number I 5 with the electrode l6 tightly sealed therein. Lower body portion contains recess |8 into which non-conductive separator I9 is tightly fitted. Separator I9 is substantially cylindrical in shape and is pointed at its lower end. Electrode H5 is curved orbent so that its terminus containing recess or hole 20 is adjacent to separator l9. A tension is placed on the terminal portion of electrode l6 which tends to thrust the sparking surface of the electrode toward lower body portion IT. The non-conductive separator I9 is of greater diameter than recess 20 so that the topmost edges of recess 20 impinge upon the beveled or sloping surfaces ofthe pointed end portion of separator l9, thus tending to hold the electrodes apart. In operation the electrodes and non-conductive separator as represented by this embodiment of my invention function the same as the electrodes and non-conductive separator in Figure 1.

Figure 3 is another fragmentary vertical cross-sectionalview of another embodiment of w my inventionin which the insulator l5, electrode l6 and lower body'portion are the same as in The difference here is in the-size of of non-conductive separator 2|. As shown iin the drawing, the separator 2| has substantially cylindrical portions which fit relatively loosely within recess l8 and recess or hole 20. The centralportion of separator 2| is enlarged to present sloping surfaces above and below which impinge upon the right-angled periphery of recess l8 and against the similar outer periphery of recess 20, thus keeping the electrode 5 at a constant distance from lower body portion I! as This can readily be --ac-' the spring action in electrode l6 tends to press it against the separator 2|. The outer diameter of separator 2| at its enlarged central portion must be greater than the inside diameter of recess I8 and recess so that the separator will not become detached from its position between the electrodes, and so that its sloping surfaces will reach the periphery of the recesses. The central enlarged portion of separator 2| may take the form defined by rotating an isosceles triangle 360 about its base line.

The embodiment of my invention shown in Figure 3 has the distinct advantage of providing for automatic adjustment of the distance between the electrode surface regardless of wear or disintegration of either or both of the sparking surfaces of the electrodes.

Figure 4 is a longitudinal cross-sectional view through the center of another form which my spark plug may assume. In Figure 4 the lower body portion of the spark plug is represented by number 25 having rigid electrode portion 26 firmly fitted therein; Number 21 represents the insulator which is held within lower body portion 25 by the action of upper body portion 28 which is threaded to fit within lower body portion 25 and adapted to press upon heat resistant gasket seal rings 29 to form a gas-tight seal about the enlarged center portion of insulator 21. Within the top center portion of insulator 21 is sealed bushing 30 which has a central threaded portion having a common axis with electrode 3|. Bushing 30 is formed within insulator 21 by any of the known molding processes to form a gas-tight seal therewith. Electrode 3|, passing through the center ofinsulator 2! and bushing 30, has a threaded portion to match the threaded portion of bushing 30. Electrode 3| is, therefore, free to revolve within insulator 2'! and by turning knurled thumb wheel 32 can becaused to be raised or lowered therein. Electrode 3| may be fitted with a locknut (not shown) to insure retention of the electrode in any desired position and prevent vertical displacement due to engine vibration. A gas-tight seal must be formed around electrode 3|. This seal may take any form which serves the purpose efficiently. I

a seal against electrode 3 Nut 35 is provided at the upper end of electrode 3| for securing the distributor wire thereto.

Referring now to the spark gap area of my spark plug as shown in Figure 4, it can be seen that electrode SI and electrode 26 both contain recesses, represented by numbers 36 and 31, respectively. These recesses are cylindrical in shape and uniform in diameter. The non-conductive separator 38 fits between the two electrodes in such a manner that its sloping surfaces bind upon the peripheral inner edges of the recesses. Thus as the sparking surface of the electrodes wears away, it is possible to keep a constant spark gap by merely turning knurled thumb wheel 32 to lower electrode 3| against the sloping surfaces of non-conductive separator 38. This adjustment can become one of the routine checks made by one man as he inspects the engine during operation.

Figure 5 is a cross-sectional view of my spark plug which is substantially the same as Figure l with theexception: of the central :electrodesand the anon-conductive separator. In: Figure 5; .I show the central electrode 40 with coil spring'Al as an integral-partithereof. The upper part of electrode 40 is tightly sealed within the insulator while the spring and the lowerpart of electrode-:-4!1,-.repres.ented by number 4-2 are free to move longitudinally within theinsulator. Non-- conductive separator43...is lodgedin recesses in the ends of the 'two electrodes. The recesses in both el'ectrodes re sufiicientl y'deep to permitthe separator to. move inwardly as 1 the electrode becomes eroded. The ction of spring 4| eliminates manual adjustment of electrode 40 and maintains constant contact of the wearing surfaces of the electrodes with the sloping surfaces of nonconductive separator 43.

My invention is not to be limited to the relative size or shape or function of the various parts of the spark plug. The materials of construction may also be any suitable material for the purposes intended. Mention has been made of recesses within the electrodes which function both to hold the separators firmly or may function as retaining guides for the protruding portions of the separator. The size of these recesses may vary from .020 to .040 inch in diameter depending on the diameter of the electrodes, and from 0.02 to 0.25 inch in depth. The outer diameter of the non-conductive separators used may vary within a wide range; however, the portion outside the recess must be greater in diameter than the recesses with which they are used in order to provide a sloping surface to impinge upon the wearing surface of the electrode.

Thus far in the disclosure of my invention, I have referred to a non-conductive separator aflixed between movable or spring activated electrodes. This non-conductive separator may be formed from any material which offers a high resistance to the passage of an electric current. One very suitable substance of which these separators may be formed is synthetic sapphire. Sapphire has a high electrical resistance and does not exhibit the tendency to accumulate carbon on its surface during use. Any non-conductive material which will offer a comparable resistance to the passage of an electric current, which will withstand the severe conditions within the internal combustion engine firing chamber and which has no substantial tendency to form encrustations on its surface may be used. Examples of such other materials are aluminum oxide, quartz, glass, diamond, emerald, mica, corundum, ruby, amethyst and picotite (black mica). My invention is not to be limited to the particular size or shape of the non-conductive separator inserted between the electrodes. In one form of my invention, I contemplate the use of a spherical separator between the electrodes. Various shapes of separators other than those I have described may be used within the scope of my invention as long as the separator functions to gradually allow the electrodes to'move toward each other as their wearing surfaces disintegrate.

What is claimed:

1. A sparking device comprising at least two electrodes spaced in sparking relationship to each other, at least one of said electrodes having a recess in its wearing surface, a non-conductive separator held between said electrodes, said separator resting on the periphery of said recess, said separator having the surface of said separator tapering outwardly from a point located within said recess, said electrodes being under tension: toward ieachuother and:v said. separator holding said electrodesz atita.substantially constant sparking distance from each other.

2. .A- sparking device in: accordance with claim 1 in which the noneconductive separator is synthetic sapphire.

3.. A: spark plugcomprisingpa. ceramic body carrying two electrodes; one a circumferential electrode surrounding said ceramic 'body' and the other a centrally mounted electrode within said ceramic body, saidzcentrally mounted. electrode having. an active endzjuxtaposed. insparking. relationship with an active portion of said circumferential electrode, a sapphire insulating means securely held to said circumferential electrode at said active portion thereof, said centrally located electrode having a recess in its active end, said sapphire insulating means having an inclined surface which impinges on the periphery of said recess and maintains said centrally located electrode in substantially constant sparking distance from said circumferential electrode.

4. A spark plug comprising a ceramic body carrying two electrodes, one a circumferential electrode surrounding said ceramic body and the other a centrally mounted electrode Within said ceramic body; said centrally mounted electrode having an active end juxtaposed in sparking relationship with an active portion of said circumferential electrode, said centrally mounted electrode having a recess in its active portion, a sapphire insulating means having recess-engaging members at its ends and having inclined surfaces in a central portion larger in diameter than the diameter of said recesses, said sapphire insulating means inserted between said electrodes with said recess-engaging members within said recesses and said inclined surfaces impinging on the periphery of said recesses.

5. A spark plug comprising a ceramic body carrying a centrally mounted electrode, a body portion surrounding said ceramic body and carrying a second electrode With a recess at its active end, said centrally mounted electrode having three conductively connected sections, a section sealed Within said ceramic body, a spring section free to move longitudinally within said ceramic body and a longitudinally movable section having an active end with a recess therein, the active ends of both of said electrodes being juxtaposed in sparking relationship with one another, a sapphire insulating means having inclined surfaces, said sapphire insulating means inserted between said active ends of said electrodes displacing said longitudinally movable section of said centrally mounted electrode against said spring section, said inclined surfaces impinging against the peripheries of said recesses.

6. A spark plug comprising a ceramic body carrying a'centrally and slidably mounted electrode, said electrode having a recess in its active end, a thumb wheel at the opposite end and having a screw thread between its ends, said screw thread engaging a threaded bushing secured within said ceramic body, a body portion carrying a second electrode with a recess at its active end, said body portion surrounding said ceramic body, said centrally mounted electrode having its active end juxtaposed in sparking relationship with said active end of said second electrode, a sapphire insulating means inserted between said electrodes with its inclined surfaces engaging the peripheries of said recesses whereby to maintain a constant spark gap between the active ends of said electrodes as said active ends erode and said centrally mounted electrode is turned down by means of said thumb wheel.

'7. A spark plug comprising a ceramic body carrying a centrally mounted electrode, a body portion carrying a second electrode with a recess in its active end, said body portion surrounding said ceramic body, said centrally mounted electrode having an active end juxtaposed in sparking relationship with the active end of said second electrode, a sapphire insulating means fastened to said active end of said centrally mounted electrode, said sapphire insulating means having an Number REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date 1,405,701 White Feb. 7, 1922 

